The present invention is directed to a process and a device used in anchoring a fastening member in a borehole formed in a hard receiving material, such as rock, concrete, brick or the like, by using a flowable hardenable material, preferably a multi-component mass.
Basically, two different processes are used for anchoring fastening members in a flowable hardenable mass.
In one process, the components forming the mass are located in separate parts of a destructible container. The container is inserted into a borehole and the container is broken by driving a fastening member into the borehole. By turning the fastening member as it is driven in, a thorough mixing of the components is achieved in the borehole. The movement of the mass injected into the borehole picks up the drilling dust remaining on the borehole surface after it has been cleaned so that the dust forms a filler material in the hardenable mass. To the extent that the drilling dust is adequately removed from the borehole in this known process, a good adhesive bond of the hardenable mass with the borehole surfaces takes place. This process can be economically justified for the placement of single fastening members. The fabrication of the container, however, is relatively complicated and, as a result, expensive. Moreover, the time required to carry out the mixing process is so great that the method is not economical for quantity production.
In the other process, the components of the flowable hardenable material are stored in separate containers positioned within a mixing and metering device. The containers hold enough of the hardenable mass for anchoring a plurality of the fastening members. The separate components are mixed together directly before they are dispensed from the device and are introduced into the borehole as a mixture of the hardenable mass. After the mass is injected into the borehole, the fastening member can be inserted into the borehole where it is to be anchored without any complicated auxiliary placement means and with a partial displacement of the hardenable mass from the borehole. In this method there is relatively little relative movement of the hardenable mass with respect to the borehole surface.
From actual practice it has been noted, even after an intensive cleaning of the borehole, that a portion of the drillings produced during the formation of the borehole still adhere to the borehole surface. Such drillings or drilling dust form a layer separating the hardenable mass from the surface of the borehole in the receiving material. Such a situation leads to regions of reduced strength within the borehole. As a result, the anchored strength of the fastening members is likely to be considerably reduced. The anchored strength, however, can only be determined after the fastening member has been secured and stressed.